I can understand that but I also take the fuzzybuns to regular check-ups and am in great contact with one of their vets as she is also a friend of mine.
They have two vets, a holistic vet and a "regular" vet (my friend)...both know the diets and both wholeheartily approve saying "if it's not broke, don't fix it".

None of my cats are ever sick...no diarrhea and no vomiting and as I mentioned, many of my past cats have lived into their late teens and early 20s and were healthy. My mom has a healthy 18 year old on the same foods.
Now Toby's brother Gus, my sisinlaw has him, was sick for his first 8 months on Iams, Science Hill and another food. His vet pretty much gave up and said to "try Kit-n-Kaboodle or something". Besides the fact that she was disgusted with this vet, she tried it and he hasn't been sick again.

Please don't think I'm arguing over who's right or who's wrong...I guess I just don't understand how these foods can be bad if I have three very healthy, active and clear eyed cats, not to mention the past kitties and others, that eat nothing other than Meow Mix and 9-Lives.